This invention relates to temperature-indicating devices and more particularly to instruments for storing a representation of the maximum temperature occurring in an adjacent region during an interval of time.
The invention may be used, for example, to record the highest temperature reached by the coolant or lubricant of an engine and may be used for similar purposes in conjunction with vehicle transmissions, torque converters or hydraulic systems and the like.
Internal combustion engines, transmissions, implement hydraulic systems and certain other fluid-containing devices as used in vehicles or elsewhere are usually equipped with a temperature-indicator of the form that displays a reading that changes as system fluid temperature changes or, in other cases, which lights an indicator lamp or the like if temperature exceeds a predetermined value. These devices alert the operator to possible malfunction or a need for maintenance procedures. They do not provide a very satisfactory means of determining the maximum temperature reached over an extended period of time such as several weeks or months. While this information might be theoretically available from the dial type of indicator, the operator does not as a practical matter continually watch the indicator nor necessarily make the kind of prolonged recording of readings which would be required.
Information on maximum fluid temperature during a long period of time may be of interest to the operator of a vehicle or the like and to maintenance personnel but may be of even more significance to vehicle component designers. An engine, for example, is manufactured with a cooling system, variously including radiators, fans, coolant pumps and the like which components contribute significantly to the bulk, weight, complication and cost of the engine. This system is initially designed to have some predetermined cooling capacity based on an estimate of what is expected to be the maximum cooling requirements in use. If it develops that insufficient cooling capacity was provided, that quickly becomes evident to operators and that information is usually soon relayed back to the manufacturer. However, the converse is not necessarily true.
If an engine has been provided with more cooling capacity than is actually necessary under the working conditions to which it is eventually put, that fact may not become known to the manufacturer for a very long period if at all.
At first consideration, it might appear that the presence of excess cooling capacity would not be a disadvantage but this is not the case when practical considerations are taken into account. Excess cooling capacity means that there is excess weight, bulk and complication in the vehicle and that fuel consumption is unnecessarily high. It also means that the cost of the engine has been made unnecessarily high.
To enable manufacturers to learn of a situation where a particular engine model is being produced with more cooling capacity than is needed for the uses to which the engine is typically being put, there is a need for a compact, rugged, economical device which can be installed on a representative sampling of such engines for a sizable period of time and which will detect and store indications of the maximum temperatures reached by the engines during that period. Copending application Ser. No. 705,845 of the present applicant, filed July 16, 1976 and entitled MAXIMUM TEMPERATURE RANGE INDICATOR discloses one form of instrument for this purpose in which successively higher temperatures change the effective electrical resistance of a resistor. An ohmmeter or similar electrical instrument is needed in order to read out the stored temperature data.